Almond meal is ground blanch almonds. You can find almond meal at health food stores. If you can’t find any you can grind them up yourself. Buy some almonds from your food store. First you will boil them and then peel of their skins. Then toast them in your oven at 250F for 10 minutes. Let cool and chop them up in your food processor.

Can I use any brand of confectioners’ sugar/powdered sugar?

Any brand will do, but the cheaper it is, the more likely the quality grade of the sugar is very low. The lower it is, the more cornstarch there is. The cornstarch helps balance the moisture to ensure that the shells of your macarons are sturdy. So it is okay to have a little cornstarch, the less the better.